1. Field of the Invention
The present invention relates generally to a metal plate, such as steel plate, with a surface decorative pattern. More specifically, the invention relates to a patterned metal plate having a dulled decorative pattern on its surface. The invention also relates to a method for producing the patterned metal plate. Further particularly, the invention relates to a method for producing a decoratively patterned, corrosion resistant and weather resistant metal strip.
2. Description of the Background Art
Because of their cool appearance, plated metal plates, such as tin plate, chromium plating galvanized plates and so forth, are rarely used in a form exposing the bare surface thereof. In order to make the metal plates useful, it is usual to print or paint desired pattern on a surface of the metal plate. This requires a printing or painting process to increase the production cost for such plate.
In another approach for giving the metal plate a higher commercial value, metal plates with an emboss-treated surface have been proposed. Uneven emboss pattern is formed on the metal plate surface for providing a cube effect, with natural feeling and shade for giving a better quality feeling. Nowadays, three types of emboss patterned metal plates have been developed and proposed.
For example, the Japanese Patent First (unexamined) Publication (Tokkai) Showa No. 51-7356 and the Japanese Patent First (unexamined) Publication (Tokkai) Showa No. 53-88080 discloses a metal plates, on which surfaces are treated by metallic plating. On the metallic plating layer, an emboss patterned transparent layer is formed. In the alternative, the metallic plated surface is coated by a transparent layer. Emboss treatment is performed for the transparent layer. Such metal plates are provided corrosion resistance and rust-proofing ability by the transparent layer, and have a bright or glossy appearance.
Though such process may provide satisfactorily high quality of metal plate with decorative uneven pattern, the production process requires various extra steps. This binders the process to be applied for mass-production and causes high production cost.
On the other hand, the Japanese Patent First (unexamined) Publication (Tokkai) Showa 53-55454 proposes to provide an emboss pattern on the surface of the metal plate, on which surface metallic plating or resin coating layer is formed by rolling utilizing a roll on which a surface emboss treatment in a desired pattern is formed. The metal plate is thus formed with an uneven emboss pattern corresponding to the emboss pattern of the peripheral surface of the roll. The metal plate thus produced may have a cube effect. Tokkai Showa No. 53-55454 further proposed to provide a top-to-bottom height difference in the projecting portion and a depressed portion within a range of 10 .mu.m to 400 .mu.m and a surface roughness greater than or equal to 5S. By controlling such controlled magnitude of roughness on the surface, the metal plate surface may be provided definite pattern with contrast in brightness.
In this process, the plated layer and surface coating layer as subjected to a rolling process tends to expand together with the metal plate to cause cracking and pin holes to degrade its corrosion resistance and rust-proofing ability. Furthermore, when the metal plate is thin, the embossed uneven pattern may be formed, forming unevenness on the opposite surface. This narrows the usage.
The Japanese Patent First (unexamined) Publication (Tokkai) Showa No. 52-118819 discloses a metal plate, bare surface of which is emboss-treated to form an uneven pattern. On the emboss-treated surface, a surface protective layer is formed.
This method is generally applicable for forming a random uneven pattern and is difficult to form the desired uneven pattern. In the alternative, in order to form the desired uneven pattern, it is essential to have a roll having a surface formed with a desired uneven pattern on the periphery. Therefore, for forming a desired or regular pattern of unevenness has to be formed on the peripheral surface of the roll.
Emboss-treatment on the metal plate is generally performed by means of a dull roll having a surface formed with a desired uneven pattern to be transferred on the metal plate surface. For forming the desired pattern of unevenness on the peripheral surface of the roll, a photoetching process as disclosed in the Japanese Patent First (unexamined) Publication (Tokkai) Showa No. 50-39235 for example, and mechanical treatment as disclosed in the Japanese Patent First (unexamined) Publication (Tokkai) Showa 50-161451, the Japanese Patent First (unexamined) Publication (Tokkai) 54-130460 for example are proposed. The photoetching process is complicated and thus causes substantial cost in production of the roll. Mechanical treatment is less expensive in comparison with photoetching. However, mechanical treatment can form only a random pattern of unevenness on the peripheral surface of the roll. Furthermore, since a sufficient magnitude of unevenness cannot be formed by the process of photoetching, light shot dull treatment is performed on the surface of the metal plate. Thereafter, dulling treatment for forming projecting unevenness or depressing unevenness which has greater area as a result of shot dull treatment for providing greater contrast. In the alternative, mat finishing is performed for the depressed portion of the metal plate.
On the other hand, the Japanese Patent First (unexamined) Publication (Tokkai) Showa No. 61-14901 discloses formation of the dulled roll by shot blasting process with masking of the desired uneven pattern. This masking process tends to require extra step in treatment.